The Homeland Security Secretary was confident in stating that this additional security screening will not hinder or restrict lawful trade, commerce or tourism in any way. The intent of implementing this screening procedure was to minutely filter out the people who could pose potential risk to the States.
There are a total of 39 countries that fall under the U.S. Visa Waiver Program. Andorra, Australia, Austria, Belgium, Brunei, Chile, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, Netherlands, New Zealand, Norway, Poland, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom are the counties whose citizens are eligible for a visa-free entry into the United States.
ESTA does not guarantee unrestricted entry into the States. It simply implies that a person is eligible to travel to U.S. The final decision is made by the US Customs and Border Protection Officer at the point of entry regarding eligibility.